1. Field of the Invention
The present invention relates to a resin sealing type semiconductor apparatus in which a power transistor or power IC having large power or generating a large amount of heat at the time of operation is installed. More particularly, this invention relates to outer leads of a semiconductor apparatus.
2. Description of the Related Art
Conventionally, products having many electronic parts mounted in a hybrid type on a printed circuit board have been used. Recently, there are module products on the market which have electronic parts including semiconductor devices installed in a lead frame system. The module products us SIP (Single In Line Package) type lead frames and a wide variety of electronic parts can be installed on each product.
In a module product assembled as resin sealing type semiconductor apparatus by using an SIP type lead frame, inner leads formed on the SIP lead frame by subjecting this frame to a resin sealing step through the transfer mold method are led out from the sealing resin layer, so that the led-out portions of the inner leads serve as outer leads. (Hereinafter, the sealing resin layer including these outer leads will be called "package.")
When a semiconductor device that has large power or generates a large amount of heat at the time of operation, i.e., a power transistor or power IC is used as in the above case, the dielectric strength should be considered. As shown in FIG. 1, a pitch P, 2P and 4P is the distance between the leads. A typical measure against the dielectric strength is to increase the pitches between the outer leads while making the remaining pitches the same. Alternatively, there is a type which has one pitch between leads increased or a type which has three different pitches between leads.
FIGS. 1 through 5B exemplify the above three prior art devices.
FIG. 1 is a perspective view of a photocoupler which performs a zero cross function and has three different pitches, the smallest, reference pitch P and its integer-multiple pitches 2P and 4P between outer leads 2 led out from a sealing resin layer 1. FIG. 2 exemplifies a type having two pitches, P and 2P, between outer leads 2 which are characterized in that their free ends have a smaller diameter. FIGS. 3 to 5B illustrate other examples. As described above, a resin sealing type semiconductor apparatus requires that the pitches between outer leads be increased in light of the dielectric strength necessary for the power element installed in the package and that the pitches between outer leads of other semiconductor apparatuses constituting a power element control section should also be increased. Further, with an SIP type lead frame in use, the outer leads are led out from one direction.
The number of outer leads and the pitches between the leads are restricted by the size of the package, thus hindering realization of multi-functions (multi-pins) of the resin sealing type semiconductor apparatus. With an SIP lead frame in use, mounted semiconductor devices are supported by the inner leads alone. When the strength of the inner leads or outer leads is not strong, the leads may deform during assembling of the apparatus.